The present invention relates to a radiation detector used for radiation imaging and a manufacturing method thereof and, more particularly, to a compact dental radiation detector used upon insertion into an oral cavity and a manufacturing method thereof.
X-ray image sensors using a CCD instead of an X-ray sensitive film are becoming popular as a medical X-ray diagnostic apparatus. In such a radiation imaging system, a radiation detection device having a plurality of pixels acquires two-dimensional image data by radiation as an electrical signal, and this signal is processed by a processor and displayed on a monitor.
As a dental radiation detector used upon insertion into an oral cavity, a radiation detector which is disclosed in JP 10-282243 A has been known. In this radiation detector, an FOP (Fiber Optical Plate) with a scintillator is stuck on the light-receiving surface of a CCD. The radiation detector has a mechanism to convert incident radiation into light by the scintillator, guide the light to the CCD by the FOP, and detect the light.
A dental radiation detector used upon insertion into an oral cavity requires a larger imaging area while downsizing and thinning the whole detector. In the above apparatus, thinning is limited in the presence of the FOP. As disclosed in WO98/36291, a scheme for thinning the detector by directly forming a scintillator on the light-receiving surface of an imaging element is considered. However, when a light-receiving portion is formed on the entire light-receiving surface, it is difficult to uniformly form the scintillator on the entire light-receiving portion, thus decreasing the output and resolution of end portions. This makes it difficult to attain the large imaging area.
It is an object of the present invention to provide a radiation detector which can attain both a small, thin structure and a large imaging area, and can be easily manufactured, and manufacturing method thereof.
To solve the above problems, a radiation detector according to the present invention comprises (1) a solid-state imaging element having a light-receiving portion where a plurality of photoelectric conversion elements are arranged, and electrode pads electrically connected to the photoelectric conversion elements, (2) a scintillator formed on a surface of the light-receiving portion of the solid-state imaging element, and (3) a substrate having a support surface for mounting the solid-state imaging element thereon, and a positioning portion which is adjacent to the support surface and projects higher than the support surface to position the solid-state imaging element with a side wall, wherein the positioning portion is formed such that the light-receiving surface of the solid-state imaging element projects toward a light incident side higher than an upper surface of the positioning portion.
On the other hand, a radiation detector manufacturing method according to the present invention comprises the steps of: (1) preparing a solid-state imaging element having a light-receiving portion where a plurality of photoelectric conversion elements are arranged, and electrode pads electrically connected to the photoelectric conversion elements, and a substrate having a positioning portion which is adjacent to a support surface, and projects higher than the support surface, (2) mounting and fixing the solid-state imaging element on the support surface of the substrate such that the light-receiving surface of the solid-state imaging element projects higher than an upper surface of the positioning portion by using a side wall of the positioning portion, and (3) forming a scintillator on the surface of the light-receiving portion of the solid-state imaging element.
In this manner, in the radiation detector according to the present invention, the solid-state imaging element is accurately positioned and fixed on the support surface of the substrate by using the positioning portion formed on the substrate. After positioning and fixing the solid-state imaging element, the scintillator is formed on the surface of the light-receiving portion of the solid-state imaging element by vapor deposition or the like. At this time, the surface of the light-receiving portion projects the most toward the light incident side. Hence, no projecting portion which becomes an obstacle is formed on the light-receiving portion in forming the scintillator, thereby uniformly forming the scintillator on the entire light-receiving portion. This can ensure the resolution and attain the large area of the effective light-receiving portion. The FOP is not used, thus facilitating thinning the detector.
The substrate further has the external connection electrodes and the electrode pads which are arranged on the upper surface of the positioning portion, and electrically connected to the external connection electrodes, and further has the wiring lines which connect the electrode pads of the solid-state imaging element and the electrode pads of the substrate, respectively. This facilitates connecting connection lines to external devices.